It is common practice in the manufacture of metal structures, for example, roll-over protective structures (ROPS) for earthmoving vehicles, to utilize welding for connection of various elements of the structure. It is also known that such structures may include one or more tubular members such that access to the interior of the welded structure is severely restricted or not possible. Welding of metals involves large amounts of heat which propagates to metal immediately adjacent the welded joint. Such heat may introduce deleterious changes in the microstructure of the metal thus affecting the overall strength and durability of the welded joint.
While fully fabricated ROPS structures are known it is necessary to join the members by welding in the corner areas. As a result numerous external gussets and corner brackets are required to provide suitable strength in the corners to withstand the forces to which the structure may be subjected. This results in a very labor intensive process to fabricate the structure with attendant high cost, both in materials and labor.
It is also known to utilize cast corner members to reduce the number of parts and the amount of welding required in manufacture of large structures such as a ROPS. Such cast corners normally include a short pilot portion disposed within the connecting tubular members to initially align the members and provide back-up for the weld process. The inner ends of the pilot portions create, with the tubular member, an abrupt change in section of the material in the heat affected zone of the material near the weld.
As large external loads are applied to the structure any deflection or bending of the tubular members tends to occur at the abrupt change in section (stress concentration) at the end of the pilot portion. Severe bending in this area may result in cracks or premature failure through the heat affected zone due to the altered microstructure therein.
U.S. Pat No. 5,280,955 issued to Peter M. Nelson on Jan. 25, 1994 and is commonly assigned to the assignee of the instant application. This patent discloses a ROPS with cast corner members having relieved portions 48 and 50 that define reduced cross-sectional areas. The reduced cross-sectional areas provide very predictable deformation and, therefore deformation of the overall structure may also be predictable. This patent also discloses in FIG. 2 a generally rectangular projection 52 which serves to pilot the two components and to provide backup for the weld between the two components similar to that described above.
It is desirable that a structure for a weld joint be provided to achieve a more gradual change in section in the area of the heat affected zone adjacent the weld to reduce strain therein due to bending under heavy load.
The present invention is directed to overcoming one or more of the problems as set forth above.